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\usepackage{booktabs}
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\begin{document}
\begin{table}[t] 
\centering 
\normalsize 
\begin{tabular}{lcccc} 
\toprule \toprule 
 & \multicolumn{2}{c}{All Mentions} & \multicolumn{2}{c}{Using City Name Filter} \\[2mm] 
 & Relative    & Relative     & Relative    & Relative     \\ 
 & Coverage of & Coverage of  & Coverage of & Coverage of  \\ 
 & Mayor       & City Manager & Mayor       & City Manager \\ 
\midrule 
 Council-Manager  &  -0.18  &  0.18  &  -0.25  &  0.29  \\ 
 \quad Govt Form  & (0.02) & (0.02) & (0.04) & (0.03) \\[2mm] 
 N                &  3540  &  3540  &  2376  &  2376  \\[2mm] 
 City Fixed Effects & Yes & Yes & Yes & Yes \\
 Year Fixed Effects & Yes & Yes & Yes & Yes \\
\bottomrule \bottomrule 
\multicolumn{5}{p{.80\textwidth}}{Standard errors, clustered by city, are in parentheses.} \\ 
\end{tabular} 
\end{table} 
\end{document}
